The present invention relates to an improved method of fixing a toner by applying a wet medium.
Conventionally, there are a variety of practical methods for fixing an unfused toner on a paper surface after being transferred thereto from a photoconductor of a dry electronic copier or a laser printer, for example, including the following:
1. Thermal fixing methods: PA0 2. A pressure fixing method for fusing and fixing an unfused toner by applying pressure generated by a high-pressure roller; PA0 3. A wet fixing method for fusing and fixing an unfused toner by dissolving a thermoplastic resin (being a constituent of toner) with a solvent via a solvent atmosphere.
[1] A thermoconductive method for fusing and fixing an unfused toner with a heated roller;
[2] A radiation method for fusing and fixing an unfused toner by radiating infra-red rays or flash;
[3] A convection method for fusing and fixing an unfused toner via a heat treatment in an electric oven;
[4] A high-frequency thermal method for fusing and fixing an unfused toner by heating the water content of a medium and objective paper in an electronic microwave oven;
However, the above conventional fixing methods respectively have a variety of technical problems described below.
When applying any of the thermal fixing methods, an unfused toner cannot properly be fixed onto all the objective surfaces except for those which are having specific sizes. Concretely, a proper heating means is essential to implement the thermal fixing method. However, because of technically difficult aspects, a large heating means cannot be applied. For instance, whenever drawing an image on a large-sized paper such as the A1 or A0 class, the image must be drawn on the paper surface directly with ink of a slow-moving pen-plotter.
On the other hand, since the above-cited pressure fixing method necessarily applies such a high pressure being more than scores of kilogram per square centimeter, the operator is obliged to introduce large-sized equipment and a soft-and-expensive resin such as a polyethylene resin or a polypropylene resin composing the toner, thus incurring a processing cost which is too expensive.
On the other hand, preceding Japanese Laid-Open Patent Application Publication No. SHO57-135966 (1982) corresponding to German Patent Application No. P3048477.6 discloses a method of fixing a toner using a wet compound. Concretely, as shown in FIG. 7, according to this prior art, by initially passing a paper 101 bearing a transferred image of an unfused toner through a container 102 filled with vaporized solvent, the produced image is fixed on the paper surface 101 by dissolving the toner with a solvent. According to this method, a lesser amount of electric power is consumed for the toner fusing process to save energy cost. Nevertheless, since acetone or toluene are inflammable and toxic solvents, the use of such a toner poses safety problems. Furthermore, not only resinous components, but also antistatic agents, and pigments such as carbon black or dyestuffs, are also used in such toners. In consequence, when such a system for immersing a toner in a solvent such as acetone or toluene is introduced, the solvent may dissolve the image on the paper surface, causing it to run, thus restraining the effective scope of the available toner components.